I'm not sure the report/article answers that, but it says:
"... extended periods of calm punctuated with spasms of selling known as flash crashes. Recent examples include a nearly 1,600 point intraday drop in February and a 1,100 point decline in August 2015."
What kind of 168 page report fails to mention the index or the day for that kind of information? References would be nice, but they could start with not being so vague.